1. Technical Field of the Invention
The invention relates to partly new compounds which are useful as pharmaceuticals, to pharmaceutical and cosmetical compositions containing new compounds and to such compounds for the use in the treatment and prevention of pathophysiological conditions and diseases either mediated or influenced by heat shock proteins (Hsps) also termed stress proteins. More particularly the invention relates to certain 1,4-dihydropyridines with selective Hsp modulating activity both in vitro and in vivo, and to the use of such compounds in the field of the treatment and prevention of pathophysiological conditions mediated by Hsps, including for example neurodegenerative diseases, cancer, metabolic syndromes, diabetes, obesity, inflammation and skin diseases, as well as diseases and/or disorders that would benefit from altered Hsp function in various metabolic or environmental stress conditions and to pharmaceutical and cosmetical compositions comprising such compounds.
2. Description of the Prior Art
Heat shock proteins (Hsps) belong to functionally related proteins whose cellular amount changes when cells are exposed to elevated temperatures or other stresses (Goldberg et al., Nature, 426: 895-899, 2003) ranging from hypoxia, inflammation, or infections to environmental pollutants. Certain Hsps may also function as molecular chaperones under normal stress-free conditions by regulating the correct folding and function of numerous important cellular proteins.
Major heat-shock proteins are grouped according to their molecular weight (Hsp 100, Hsp 90, Hsp70, Hsp60, and the “small Hsps”, sHsps).
Some members of the Hsp family are expressed at low to moderate levels in all organisms because of their essential role in protein maintenance. Due to their multiple and vital functions, Hsps play fundamental roles in the aetiology of several human diseases (Solti et al., Br. J. Pharmacol., 146: 769-780, 2005). For example aberrantly high levels of either the overall array of Hsps, or certain Hsp classes are characteristic in different cancer cells and the converse applies typically for type 2 diabetes, neurodegeneration, cardiovascular diseases or aging (Vigh et al.; Prog. Lipid Res., 44(5): 303-344, 2005 and Vigh et al.; Trends Biochem. Sci., 32: 357-363, 2007).
In order to highlight the mechanism of action of the different Hsp classes and to provide compounds moderating their activity and being suitable for drug development a large number of investigations have been undertaken over the last decade.
Hsp 70
The evolutionary conserved Hsp70 chaperone family and its co-chaperones with the exception of some archaea (Large et al., Biochem. Soc. Trans. 37: 46-51, 2009), are present in all ATP-containing compartments of living organisms (Macario et al., Genetics, 152:1277-1283, 1999). The functional Hsp70 chaperone network entails ATP-driven interactions among many diverse substrate-specific and less specific J-domain co-chaperones (49 in human) that target the fewer Hsp70 isoforms (Kamping a et al., Cell Stress Chaperones, 14:105-111, 2009) onto hundreds of protein substrates in the cell and are regulated by various nucleotide exchange factors such as glucose regulated protein E (GrpE) (Harrison, Cell Stress Chaperones 8:218-224, 2003), BAG (Kabbage et al., Cell Mol Life Sci., 65: 1390-1402, 2008), HspBP1 (Kabani et al., FEBS Lett., 531:339-342, 2002), and Hsp110 proteins (Shaner et al., Cell Stress Chaperones, 12:1-8, 2007). These networks are crucial to the co-translational folding of nascent polypeptides, the remodelling of native protein complexes, the transduction of cellular signals, the regulation of the cell cycle, proliferation and apoptosis (Jolly et al., J. Natl. Cancer Inst., 92:1564-1572, 2000), the regulation of the heat shock response, the unfolding and refolding of stress-denatured proteins, and the import of proteins into the mitochondria (De Los Rios et al., Proc Natl Acad Sci USA, 103:6166-6171, 2006), chloroplasts (Shi et al., Plant Cell, 22:205-220, 2010), and the endoplasmic reticulum (reviewed in Zimmermann et al., Biochim Biophys Acta, 1808:912-924, 2011).
In normal cells, quality control systems prevent the accumulation of toxic misfolded protein species. However, in response to mutagenesis, aging or oxidative stress, misfolding can often occur escaping quality control (Soskic et al., Exp. Gerontol., 43: 247-257, 2008; Zeng et al., Mech. Ageing Dev., 126: 760-766, 2005; Shpund & Gershon, Arch. Gerontol. Geriatr., 24: 125-131, 1997).
As postmitotic cells, neurons appear to be particularly sensitive to these effects and many neurodegenerative disorders, such as Alzheimer's, Parkinson's, and Huntington's diseases, involve aberrant accumulation of misfolded or misprocessed proteins. Genetic studies have routinely linked Hsp70 and its co-chaperones to this process, and thus, it has emerged as a potential drug target (Evans et al., J Med Chem., 53:4585-4602, 2010). Alzheimer's disease (AD) is the most common neurodegenerative disease, and its patients are characterized by progressive memory loss and the accumulation of senile plaques (SP) composed of β-amyloid (An) and neurofibrillary tangles (NFTs) assembled from tau. Current models suggest that self-association of Aβ or tau into β-sheet rich oligomers leads to neuronal cell death. Hsp70 has been shown to play important roles in the cytotoxicity of both Aβ and tau (for review see (Evans et al., J Med Chem., 53:4585-4602, 2010). For example, Hsp72 blocks the early stages of Aβ aggregation in vitro at substoichiometric levels (Evans et al., J Biol Chem., 281:33182-33191, 2006), and Hsp70 has been shown to alter processing of the amyloid precursor protein (Kumar et al., Hum Mol Genet., 16:848-864, 2007). Also, this chaperone protects against Aβ-induced cytotoxicity via inhibiting caspase-9 and accelerating the elimination of Aβ (Veereshwarayya et al., J Biol Chem., 281:29468-29478, 2006). In addition to these effects on Aβ, Hsc70 also binds tau at two sites within its tubulin-binding repeats, which is the same region required for tau self-association (Sarkar et al., J Neurosci Res., 86(12):2763-2773, 2008). This finding suggests that Hsc70 might compete with aggregation and toxicity and, consistent with this model, overexpression of Hsp70 reduces aggregated tau in mouse models (Petrucelli et al., Hum Mol Genet., 13:703-714, 2004).
Pharmacological Upregulation of Hsp70 Expression
Many pharmacological agents have been demonstrated to increase cellular expression of Hsp70 through various mechanisms (Sloan et al., Curr Opin Drug Discov Devel., 12:666-681, 2009). A distinction should, however, be made between molecules that act by a defined stimulation within the Hsp70 regulatory pathway and those that affect Hsp70 levels by introducing a cellular stress. Compounds that use the latter stress-inducing mechanism may have a higher propensity to cause cell death or other unwanted effects as a result of chronic stressing, and thus may be less desirable as therapeutic agents. A further distinction of the modes of action of different Hsp70 upregulators can be made between Hsp70 inducers, which increase Hsp70 expression under a broad range of stress conditions, and Hsp70 co-inducers, which act solely to potentiate a pre-existing stress response and have little or no effect in non-stressed or healthy systems. The co-inducer mechanism may therefore selectively exhibit an effect in diseased tissue, thereby inherently reducing the risk of unwanted side effects in healthy tissue (Sloan et al., Curr Opin Drug Discov Devel., 12:666-681, 2009).
Modulators of Protein Processing
Proteasome inhibitors such as bortezomib (Lauricella et al., Apoptosis, 11:607-625, 2006), MG-132 and lactacystin (Kim et al., Biochem Biophys Res Commun., 264:352-358, 1999) demonstrate significant HSF-1-mediated Hsp70 induction via inhibition of protein degradation, accumulation of unfolded protein and induction of the cellular stress response (Sloan et al., Curr Opin Drug Discov Devel., 12:666-681, 2009). Lactacystin selectively induces the heat shock response (HSR) in preference to the unfolded protein response, and reduces nuclear inclusions in a neuronal P127Q Huntington's disease model (Kim et al., J Neurochem., 91:1044-1056, 2004). In many cases, Hsp70 induction is accompanied by other, mechanism-based and undesirable cellular effects or apoptosis (Sloan et al., Curr Opin Drug Discov Devel., 12:666-681, 2009). Although proteasome inhibitors are approved for clinical use in oncology, their limited therapeutic window may preclude significant applicability of these drugs in the treatment of protein-folding diseases.
Chemically Reactive Inducers
Chemical induction of Hsp70 has been described about N-ethylmaleimide (Senisterra et al., Biochemistry, 36:11002-11011, 1997), electrophilic serine protease inhibitors such as 3,4-dichloroisocoumarin (DCIC) and N-a-tosyl-L-lysine chloromethyl ketone (TLCK) (Rossi et al., Biol Chem., 273:16446-16452, 1998), curcumin, a major constituent of turmeric (Dunsmore et al., Crit Care Med., 29:2199-2204, 2001), cyclopentenone PGs, characterized by PGA1, A7-PGA1, PGA2 and Δ12-PGJ2 (Lee et al., Proc Natl Acad Sci USA, 92:7207-7211, 1995).
The cyclopentenone PGs-are able to induce Hsp70 and are reported to induce HSF-1 activation (7- to 15-fold) (Hamel et al., Cell Stress Chaperones, 5:121-131, 2000). Sodium salicylate enhances Hsp70 induction in spinal cord cultures (1 mM/40° C.) compared with heat shock alone, and indomethacin reduces the temperature required for HSF-1 activation in HeLa cells under heat shock conditions at a dose of 250 μM. This activity of indomethacin correlates with an increase in HSF-1 phosphorylation and a cytoprotective effect in HeLa cells; pretreatment with indomethacin (250 μM/40° C.) improved cellular survival rate of a subsequent 44.5° C. heat shock from 3% with no pretreatment to approximately 40% (Lee et al., Proc Natl Acad Sci USA, 92:7207-7211, 1995).
Recent evidence has also suggested that PPARγ agonists may have utility other than their well-characterized insulin sensitizing effects in Hsp-dependent processes: the reduction of Hsp70 inducibility observed in the heart of an insulin-resistant rat model was ameliorated by treatment (10 mg/kg/day) with the PPARγ agonist pioglitazone. Additional reperfusion experiments also demonstrated that pioglitazone assisted functional recovery in isolated rat hearts (Taniguchi et al., Diabetes, 55: 2371-2378, 2006).
Celastrol, a quinine methide triterpene isolated from preparations used in Chinese herbal medicine, potently co-induces Hsp70 in concert with other stresses via an HSF-1-dependent mechanism (Westerheide et al., J Biol Chem., 279:56053-56060, 2004). This drug has demonstrated neuroprotection in Huntington's models of polyQ aggregation (Zhang et al., J Mol Med., 85:1421-1428, 2007), and cytoprotection in mouse transgenic models of amyotrophic lateral sclerosis (Kiaei et al., Neurodegener Dis., 2:246-254, 2005). Several other natural products including the triterpenoid enones glycyrrhizin (Yan et al., Cell Stress Chaperones, 9:378-389, 2004) and carbenoxolone (Nagayama et al., Life Sci., 69:2867-2873, 2001), as well as the masked acetal paeoniflorin (Yan et al., Cell Stress Chaperones, 9:378-389, 2004), may induce Hsp70 by similar mechanisms to celastrol.
Co-Inducing Hydroxylamine Derivatives
A family of hydroxylamine derivatives, including the prototype bimoclomol, were identified as co-inducers of the HSR with utility in a range of disease models-(Vigh et al., Nat Med., 3:1150-1154, 1997). Treatment of myogenic rat H9c2 cells with bimoclomol (10 μM) 16 h prior to heat shock resulted in a 4-fold increase in Hsp70 levels relative to heat shock alone (Vigh et al., Nat Med., 3:1150-1154, 1997), with this induction providing cytoprotection (at 100 μM) in rat neonatal cardiomyocytes undergoing a lethal heat shock (Polakowski et al., Eur J Pharmacol., 435:73-77, 2002). The mechanism of action is thought to be via binding and modulation of phosphorylation of HSF-1 leading to effects on HSF-1/DNA binding (Hargitai et al., Biochem Biophys Res Commun., 307:689-695, 2003), although additional effects related to stabilization of membranes during heat shock have been noted (Torok et al., Proc Natl Acad Sci USA, 100:3131-3136, 2003).
The bimoclomol analog BRX-220 has been demonstrated to significantly elevate Hsp70 level relative to vehicle in neurons following trauma (Kalmar et al., Exp Neurol., 176:87-97, 2002). The free base of BRX-220, arimoclomol, also delayed the progression of an amyotrophic lateral sclerosis phenotype in a mouse model (Kalmar et al., J Neurochem., 107:339-350, 2008; Kieran et al., Nat Med., 10:402-405, 2004).
Another hydroxylamine derivative NG-094 significantly ameliorated polyQ-mediated animal paralysis in C. elegans model, reduced the number of Q35-YFP aggregates and delayed polyQ-dependent acceleration of aging (Haldimann et al., J Biol Chem., 286:18784-18794, 2011).
Metabolites and Nutrients
Relatively high doses of several metabolites and nutrients have also exhibited effects on Hsp levels, with associated functional benefits: α-lipoic acid ameliorated Hsp70 deficiency in patients with Type 1 diabetes (Strokov et al., Bull Exp Biol Med., 130:986-990, 2000); and studies in brains of aged rats demonstrated increased Hsp expression (Hsp70 and heme oxygenase) in response to dosing with acetyl-1-carnitine, a compound that is found in mitochondrial membranes (Calabrese et al., Antioxid Redox Signal, 8:404-416, 2006).
Teprenone utilized in gastric ulcer treatment is a well-characterized inducer of Hsp70 that has exhibited cytoprotective benefit in several models including gastric necrosis (Tomisato et al., Biol Pharm Bull., 24:887-891, 2001), cerebral infarction (Nagai et al., Neurosci Lett., 374:183-188, 2005), hepatotoxicity (Nishida et al., Toxicology, 219(1-3):187-196, 2006) and inflammation (Mochida et al., J Clin Biochem Nutr., 41:115-123, 2007). Other chaperones, including HspB8 (Sanbe et al., PLoS ONE, 4:e5351, 2009), are also induced by teprenone, which may further contribute to the cytoprotective properties of the molecule. Carvacrol, a major compound in oil of many Origanum species, had a capacity to co-induce cellular Hsp70 expression in vitro (Wieten et al., Arthritis Rheum., 62:1026-1035, 2010). Carvacrol specifically promoted T cell recognition of endogenous Hsp70 as was shown in vitro by the activation of an Hsp70-specific T cell hybridoma and amplified T cell responses to Hsp70 in vivo (Wieten et al., Arthritis Rheum., 62:1026-1035, 2010).
Miscellaneous Hsp70 Inducers
The SirT-1 activator resveratrol induces Hsp70 and exhibits cytoprotection in response to heat shock and hydrogen peroxide treatment in human peripheral lymphocytes (Putics et al., Antioxid Redox Signal, 10:65-75, 2008).
Riluzole, an FDA approved drug for the treatment of amyotrophic lateral sclerosis, demonstrated a co-induction of Hsp70 in a reporter gene assay with heat shock. This effect, which was ablated in HSF-1 knockout cells, was thought to be caused by a stabilization of the cytosolic HSF-1 pool (Yang et al., PLoS ONE, 3:e2864, 2008).
Elesclomol has demonstrated efficacy in Phase II clinical trials for the treatment of metastatic melanoma by increasing the quantity of reactive oxygen species (ROS) in cells and selectively inducing apoptosis in hypoxic tumour cells. This effect was accompanied by a tumour cell-specific increase in hypoxic tumour cells (Revill et al., Elesclomol. Drugs Future (2008) 33:310-315), however, development of this drug was recently suspended because of safety concerns.
Other compounds that act to induce Hsp70 through sometimes incompletely characterized mechanisms include ectoine, a natural product isolated from halophilic microorganisms (Buommino et al., Cell Stress Chaperones, 10:197-203, 2005), diazoxide (O'Sullivan et al., J Neurotrauma, 24:532-546, 2007), and imidazothiadiazole (Salehi et al., Chem Biol., 13(2):213-223, 2006).
Many of the Hsp70 inducers described above may rely on the covalent modification of proteins for their mode of action, and could lead to initiation of the HSR, which may be problematic because of non-specific effects and immunogenicity. In some cases, molecules may simply be cell stressors, activating the cellular defence mechanisms including Hsp expression. This chronic stressing of cells may deliver short-term efficacy, but the long-term effects on cellular response and viability are less easily predicted. Co-inducer compounds that potentiate the response to a pre-existing stress without exhibiting effects in non-stressed environments may provide a higher degree of tissue selectivity compared with non-specific stressors by acting to potentiate pre-existing but inadequate stress responses to ongoing disease-related stress.
Genetic Upregulation of Hsp70
The augmentation of Hsp70 has demonstrated beneficial effects in several overexpression studies, and in many cases has been associated with cytoprotection or attenuation of stress-induced injury (Broome et al., FASEB J., 20:1549-1551, 2006; Choo-Kang et al., Am J Physiol Lung Cell Mol Physiol., 281:L58-68, 2001; Chung et al., Proc Natl Acad Sci USA, 105(5):1739-1744, 2008; Marber et al., J Clin Invest., 95:1446-1456, 1995; Muchowski et al., Proc Natl Acad Sci USA, 97:7841-7846, 2000; Zheng et al., J Cereb Blood Flow Metab., 28:53-63, 2008). The exposure of cells or whole organisms to temperatures in excess of 40° C. (‘heat stressing’) causes the upregulation of chaperones, including Hsp70. Many different compensatory mechanisms are activated during heat stressing, and therefore, it is difficult to assess which effects are caused solely by Hsp70. In order to overcome this challenge, mice that overexpress solely the rat Hsp70 on promotion with β-actin have been developed. In these transgenic mice the overexpression of the rat inducible 70-kD heat stress protein increases the resistance of the heart to ischemic injury (Marber et al., J Clin Invest., 95:1446-1456, 1995). In another study, Hsp72 overexpressing mice exhibited resistance to diet-induced hyperglycemia (Chung et al., Proc Natl Acad Sci USA, 105:1739-1744, 2008), and a reduction in age-related markers of oxidative stress (lipid peroxidation, glutathione content, superoxide dismutase and catalase levels) (Broome et al., FASEB J., 20:1549-1551, 2006). An increased expression (˜10-fold) of specific isoforms of Hsp70 has also been demonstrated in Hsp70 overexpressing mice, and was accompanied by a reduced susceptibility to brain ischemia/reperfusion injury (Zheng et al., J Cereb Blood Flow Metab., 28:53-63, 2008). This protection from brain ischemia was accompanied by a reduction in the activation of NFκB throughout the brain as a whole, suggesting that Hsp70 may ameliorate ischemic injury by reducing inflammatory processes (Zheng et al., J Cereb Blood Flow Metab., 28:53-63, 2008). The effect of the overexpression of Hsp70 on discrete protein-folding processes has been demonstrated in an in vitro model of Huntington's disease, the aggregation of the huntingtin protein bearing extended polyglutamine repeats was significantly reduced in yeast that overexpressed Hsp70 (or Hsp40), suggesting a direct role for these chaperones in preventing the misfolding and/or aggregation of this pathogenic protein (Muchowski et al., Proc Natl Acad Sci USA, 97:7841-7846, 2000).
Similarly, in a cell model of cystic fibrosis, trafficking of the cystic fibrosis transmembrane conductance regulator (CFTR) containing the misfolding-prone ΔF508 mutant could be normalized in IB-3 cells with plasmid-induced overexpression of Hsp70, implying that Hsp70 has a role in chaperoning and correctly folding the mutant CFTR, enabling it to be trafficked to the cell surface (Choo-Kang et al., Am J Physiol Lung Cell Mol Physiol., 281:L58-68, 2001).
Small Hsps
Unlike the ATPase chaperones Hsp100, Hsp90, Hsp70, and Hsp60, the small Hsps (sHsps) with a conserved α-crystalline domain that passively binds misfolded intermediates, independently from ATP hydrolysis (Jakob et al., J Biol Chem., 268:1517-1520, 1993). Without stress, sHsps are mostly assembled into large oligomeric complexes (Gamido et al., Cell Cycle, 5:2592-2601, 2006), which, under stress conditions, may dissociate into amphiphilic dimers that prevent misfolding polypeptides from aggregating (Jakob et al., J Biol Chem., 268:1517-1520, 1993) and protect membranes from heat disruption (Haslbeck et al., Nat Struct Mol Biol., 12:842-846, 2005; Horvath et al., Biochimica et Biophysica Acta (BBA)—Biomembranes, 1778:1653-1664, 2008). sHsps cooperate with Hsp70/Hsp40 and Hsp100 or the GroEL/GroES chaperone networks in refolding of misfolded proteins (for a review, see (Nakamoto et al., Cell Mol Life Sci., 64:294-306, 2007). Human Hsp27 and Hsp70 are often, although not obligatorily, co-expressed in response to a variety of physiological and environmental stimuli (Gamido et al., Cell Cycle, 5:2592-2601, 2006; Vigh et al., Trends Biochem Sci., 32:357-363, 2007). As sHsps have strong cytoprotective properties (Gamido et al., Cell Cycle, 5:2592-2601, 2006), their inhibition is an important target in pharmacological therapies to cancer (Didelot et al., Curr Med Chem., 14:2839-2847, 2007), whereas the upregulation sHsps may prevent liver damage (Kanemura et al., J Gastrointest Surg., 13:66-73, 2009) or pathologies caused by protein misfolding, such as Alzheimer's (Fonte et al., J Biol Chem 283:784-791, 2008; Wu et al., Neurobiol Aging, 31:1055-1058, 2010), Parkinson's (Zourlidou et al., J Neurochem., 88:1439-1448, 2004), and Huntington's disease (Perrin et al., Mol Ther., 15(5):903-911, 2007). According to a recent study Hsp27 can protect neurons against the acute and chronic toxic effects of ethanol in transgenic mouse model (Toth et al., Cell Stress and Chaperones, 15:807-817, 2010).
Although Hsp modulating small compounds are known and some of them are under clinical trials none of them has been marketed as pharmaceutically active agent so far. There remains an increasing need for specific potent Hsp modulating compounds to meet the demanding biological and pharmaceutical requirements to proceed towards human clinical trials. The ideal candidates for therapeutic use would be compounds which do not induce/silence the classical heat-shock protein response per se. Instead, they only modulate the expression of specific classes of Hsps altered by mild physical or pathophysiological stresses. Such Hsp co-modulators are unique drug candidates because they may enhance/decrease HSP expression in diseased cells, without significantly affecting healthy cells thereby less likely that they have major side effects.
Thus, principal aim of the present invention is the provision of compounds with selective stress protein modulating activity, especially co-modulating activity, whereby they are useful in the treatment of neurodegenerative disorders, cancer diseases, metabolic syndromes, lysosomal storage diseases skin diseases and additionally could be used in combinational therapies.
The present invention provides certain partly novel 1,4-dihydropyridines with selective Hsp modulating activity. It has been surprisingly and unexpectedly found that said compounds show selective Hsp co-modulating activity, which has not been described for 1,4-dihydro-pyridine derivatives so far.
A huge number of documents disclosed 1,4-dihydropyridine derivatives and their uses but none of them disclosed the use of the specific compounds of the present invention as Hsp modulators.
1,4-Dihydropyridines are particularly well known in pharmacology as L-type calcium channel blockers (Edraki et al., Drug Discovery Today, 14:1058-1066, 2009); and have been extensively used in the treatment of cardiovascular diseases (Hope & Lazzara, Adv Intern Med., 27:435-52, 1982). Calcium antagonist 1,4-dihydropyridines have been described for use in the treatment of neuropathies in diabetes (Taber, J. et al., U.S. Pat. No. 5,438,144). The derivatives of 4-(3-chlorophenyl)-5-substituted-carbamoyl-1,4-dihydropyridine-3-carboxylic acid showed selective inhibitory action of N-type calcium channel, and were effective in the treatment of acute stage of ischemic cerebrovascular disorders; progressive neurodegenerative diseases such as Alzheimer's disease, AIDS related dementia, Parkinson's disease etc. (Nakajo, A. et al., U.S. Pat. No. 6,610,717). Some ester derivatives of 4-nitrophenyl-1,4-dihydropyridine-5-phosphonic acid are useful for treating cancer or a pre-cancerous condition (Krouse, A. J., WO 2008/137107). Compounds with condensed 1,4-dihydropyridine skeleton have been reported to reduce elevated blood glucose level (Ono, M. et al., WO 2005/025507) or to prevent cancerous cells to divide (Mauger, J., et al., WO 2007/012972). 2,6-Unsubstituted-1,4-dihyropyridine derivatives possesses sirtuin deacetylase activity and may be used for the treatment of cancer, metabolic, cardiovascular, and neurodegenerative diseases (Antonello et al., J. Med. Chem., 52:5496-504, 2009). N-substituted-1,4-dihydropyridines have been reported to have coronary vasodilator and antihypertensive activity (Meyer, H. et al., HU 164867). Some N-substituted-1,4-dihydropyridine derivatives are useful in the treatment of acute and chronic ischaemic disorders by improving blood viscosity (Behner, O., EP 0 451 654), while other N-substituted derivatives showed selective Ca2+ dependent K+ channel modulating activity and were useful for the treatment of CNS disorders (Heine, H., G., EP 0 705 819 and Heine, H., G., EP 0 717 036).